Microcomponents are delivered to the processor in a magazine, where they must be removed from the magazine for assembly. In a magazine such as the one described, for instance, in German Laid Open Publication DE 197 09 136 A1, the microcomponents are integrated in the wafer-type magazine, so that they are protected from damage during transport. The microcomponents must be ejected from this magazine by means of a plunger.
For this purpose, the entire magazine wafer must first be positioned in such a way that each component that is to be removed from the magazine is exactly at the location where it is to be installed in an already existing structure of microcomponents. If, for instance, a gear unit is to be assembled from microcomponents, the corresponding gears must be positioned exactly above the shafts that are to receive them and must then be ejected from the magazine. Currently, the magazine wafers are grasped and positioned either by hand or by means of an automatically operated gripper system.
Positioning by hand decisively depends on the skill and concentration of the person involved. Positioning aids that may be arranged in the magazine can be used only to a limited extent or not at all.
In automatic gripper systems, limit stops are used, for instance, against which the edge of the magazine wafer is placed. However, due to the shrinkage of the magazine and microcomponent material that occurs during the manufacturing process, the position of the microcomponents changes. The molding tool is therefore made larger, so that this systematic shrinkage during production of the microcomponents is taken into account. Shrinkage tolerances, however, result in positional tolerances of the microcomponents within the magazine. Consequently, even those microcomponents that are arranged adjacent to the guide edge may have shifted, such that they are not arranged at the intended position within the magazine. To be able to remove a plurality of components from the wafer magazine, the magazine must be pushed back and forth by means of a displacement device, so that incorrect positions of microcomponents can add up. This has the result that the ejection tools, such as plungers or the like, are not arranged at the position where the components to be removed are actually located, or the components to be removed are not located exactly above the position where the structure receiving them is arranged. This causes damage to either the components or the magazine, or damage to the larger microstructures on which the microcomponents are to be mounted, or even damage to the ejection tools.
Optical methods, i.e. image analysis processes, are therefore already being used for the positioning of microcomponents, as described, for instance, in G. Reinhart et al., “Flexible Montage von Miniaturbauteilen” [Flexible Assembly of Miniature Components], F+M 105 (1997) 1-2, pp. 43–45. This presents the problem of insufficient contrast, however, because both the magazine and the microcomponents are made of similar materials or, if a separator is produced, even of identical materials. As a result, the position of the corresponding microcomponents cannot be determined exactly. Consequently, the required accuracy of 5 μm and better, which is often required for the precise positioning of the microcomponents, cannot be met.
A further drawback is that image recognition and analysis systems are costly and require a relatively long time for positioning because the wafer magazine or the tools must be moved in several spatial directions.
Furthermore, the wafer magazine can bend as the microcomponents are ejected, which also causes malpositioning.